664688736 has 72 divisors (see below), whose sum is σ = 1893855600. Its totient is φ = 221135616.

The previous prime is 664688681. The next prime is 664688737. The reversal of 664688736 is 637886466.

It is a tau number, because it is divible by the number of its divisors (72).

It is a super-2 number, since 2×664688736² = 883622231530555392, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664688737) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 170586 + ... + 174438.

It is an arithmetic number, because the mean of its divisors is an integer number (26303550).

Almost surely, 2^664688736 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 664688736, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (946927800).

664688736 is an abundant number, since it is smaller than the sum of its proper divisors (1229166864).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

664688736 is a wasteful number, since it uses less digits than its factorization.

664688736 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4468 (or 4457 counting only the distinct ones).

The product of its digits is 6967296, while the sum is 54.

The square root of 664688736 is about 25781.5580599777. The cubic root of 664688736 is about 872.7156681222.

The spelling of 664688736 in words is "six hundred sixty-four million, six hundred eighty-eight thousand, seven hundred thirty-six".